1. Field of the Invention
The invention relates to a device and method for switching optical signals or beams. Such a device or method may, for example, be used in telecommunications equipment, computers or screens.
2. Background Art
Optical switches are known in which several beams of light derived from a number of incoming glass fibers are deflected in a controlled manner and selectively engaged in a number of outgoing glass fibers. For this purpose retractable reflecting elements are placed in the paths of the light beams (for example, U.S. Pat. Nos. 5,841,917, 5,960,132, and 5,995,688). In addition, switches are known in which an incoming glass fiber can be offset in relation to the outgoing glass fibers (for example, U.S. Pat. Nos. 5,214,727 and 5,864,643). The mechanical construction of both types of switches is complex and the possibilities of parallel and series connection are very limited.
There are also systems utilizing reflecting elements which can be controllably rotated about one or more axes, and which can deflect a beam of light in a desired direction (for example Published International Application WO 9809289, European Patent Publication EP 0834759, and U.S. Pat. No. 5,917,647). These systems are mainly used for producing images.
Accordingly, it is desired to provide a system and method with which a number of optical signals or beams can be switched without the disadvantages and limitations of the above-mentioned optical switches.
Many of the disadvantages of the prior art can be overcome according to the invention by making use of transmissive optical elements that may be diffractive or refractive and whose orientation or position can be regulated in a controlled manner.
One embodiment of the invention is device comprising an optical element which at least partially transmits optical radiation and whose position is adjustable. Position refers here to the orientation (angle) or position (location). The optical radiation may, for example, be in the form of a digital signal or a frequency- or amplitude-modulated beam. When the position is adjusted, the orientation of the element is regulated relative to an incoming signal or beam (rotation), or possibly its position (translation). The term optical means in this case that the element interacts with the electromagnetic radiation passing through it and does not exclude optical frequencies outside the visible spectrum. In particular, it includes infrared frequencies conveyed by optical fiber. An advantage of such a device is that it is possible to use several elements in series. In principle, the number of switching possibilities (in series) is therefore nearly unlimited.
In a preferred embodiment the optical element is diffractive. It may be fabricated, for example, from a number of thin patterned layers which can be deposited on a substrate by means of a vacuum processing techniques such as sputtering or chemical vapor deposition, and formed by means of abrasive or etching techniques, whether or not combined with lithographic techniques. The advantage of using such diffractive elements is the possibility of installing a large number of elements on a small surface with a high degree of precision. This construction provides high switching density.
The optical element may also be refractive, i.e. it more resembles a classic lens whose optical effect can be described with a limited number of focal lengths.
In a preferred embodiment the optical element is connected to a movable electro-mechanical element, thus enabling the orientation, or possibly the position of the optical element to be adjusted by rotation, or possibly translation. This mechanical element can be connected to a base by means of a number of flexible mechanical components, such as torsion bars. The movable mechanical element and the other mechanical components can all be formed from a substrate using abrasive or etching techniques, whether or not combined with lithographic techniques. Here too, a large number of elements can advantageously be fabricated on a small surface area using micromechanical techniques.
In a preferred embodiment the mechanical actuation takes place by means of electrostatic forces or utilizing a piezoelectric effect. The advantage of this is that integration of the required electrodes or piezoelectric layers is possible on the same substrate.
The invention further includes an assembly of a number of such devices, in which the optical elements are installed close together in one or more planes. When the above-mentioned thin-film and etching techniques are used, densities from 100 elements per square centimeter to as much as 10,000 per square centimeter are possible.
The connection of such an assembly to a number of conductors of electromagnetic radiation, such as glass fibers, provides a device with which signals or beams can be switched.
A signal or beam deriving from a conductor drops through an optical element and is transmitted/reflected, converged/diverged and/or changes direction, whether or not dependent on the wavelength. In this case the optical parameters of the incident electromagnetic radiation (such as angle of incidence, convergence, divergence, wavelength distribution and intensity) and the geometrical parameters (such as structure, layer thickness distribution, orientation and position) and material parameters (such as refractive indices and transmission coefficient) of the optical element concerned, together determine the optical parameters of the transmitted electromagnetic radiation (such as angle of incidence, convergence, divergence, wavelength distribution and intensity). The optical parameters of the transmitted signal or beam are adjustable by means of the orientation or position of the optical element. Thus a number of signals or beams can be switched in parallel.
Where the optical elements are positioned in several planes, an optical switch is provided in which the switching possibilities are unlimited in principle.